(a) Field of the Invention
The present invention relates to an electrode active material for a secondary battery, and a secondary battery comprising the same electrode active material.
(b) Description of the Related Art
In general, a lithium secondary battery is obtained by using materials capable of lithium ion intercalation/deintercalation as a cathode and an anode, and by injecting an organic electrolyte or a polymer electrolyte between the cathode and the anode. Such a lithium secondary battery generates electric energy via redox reactions induced by the lithium ion intercalation/deintercalation at the cathode and the anode.
Currently, carbonaceous materials have been used as an electrode active material forming the anode of a lithium secondary battery. However, an electrode active material having a higher capacity is still required in order to further improve the capacity of a lithium secondary battery.
To satisfy such requirement, metals that show a higher charge/discharge capacity as compared to carbonaceous materials and are capable of forming an electrochemical alloy with lithium, such as Si, Al, etc., have been used as electrode active materials. However, such metal-based electrode active materials show a severe change in volume due to lithium intercalation/deintercalation, so that they are cracked and finely divided. Therefore, secondary batteries using such metal-based electrode active materials undergo a rapid drop in capacity during repeated charge/discharge cycles and show poor cycle life characteristics.
Japanese Laid-Open Patent No. 2001-297757 discloses an electrode active material having a structure based on an α phase comprising an element capable of lithium intercalation/deintercalation (e.g. Si) and a β phase essentially comprising an intermetallic compound or a solid solution of the above element with another element b.
However, the aforementioned electrode active materials are still insufficient in providing excellent cycle life characteristics, and thus cannot be used as practical electrode active materials for a lithium secondary battery.